Networks for wireless communication include various types of radio access technologies (RATs), for example, High Rate Packet Data (HRPD), Long Term Evolution (LTE) and Worldwide Interoperability for Wireless Access (WiMAX) types. Such diverse networks have benefits both for the network users and the network operator. The user terminal can switch to the RAT that is most suitable at the relevant time. The operator can do load-sharing between RATs so as to improve network usage and performance.
An inter-RAT handover is process in which a mobile terminal switches from using a first radio access system having a first radio access technology (such as LTE) to a second radio access system having a second radio access technology (such as WiMAX).
Standards have evolved (via standards organizations) for different wireless technologies that specify how each network element should interface with the network element so that the network elements manufactured by different vendors can work together. Each standard specifies the interfaces between network elements.
Because mobile terminals are linked to a serving network by RF signals whose origin cannot be readily identified with any degree of certainty, an important aspect of wireless communication is the establishment and maintenance of a security association between the mobile terminal and the serving network, to establish that mobile terminal identity and that it is an authorized user of the network. This security association is created with the assistance of the mobile user-subscriber's home network during initial authentication of the mobile terminal entering the network, and is normally carried out by, or under the control of an authentication server in that home network. Typically that authentication server is implemented as an Authentication, Authorization and Accounting (AAA) server. Such authentication is generally implemented via a series of security keys, either known to the participants, or exchanged among relevant network and mobile terminal entities via cryptographic hashes of the key.
Since different wireless standards specify different security mechanisms to authenticate and authorize the end user, as well as different methodologies to compute resulting session keys, the interworking among different technologies becomes a complicated issue for operators. In the art, interworking with two technologies requires that either one technology be modified to be aligned with the other technology, or that both technologies be modified to another common standard.